Industrial loaders used in the construction and mining industries have a frame which carries a loader boom. The loader boom is conventionally raised and lowered by means of a pair of hydraulic cylinders having one end connected to the loader frame section and their piston rod ends connected to transversely spaced boom arms. The boom arms are normally rigidly interconnected by one or more transverse members. The boom lift cylinders transmit large forces to the boom arms.
One way of attaching the cylinder rods to the loader arms has been to provide a yoke on the end of the cylinder rod with a transverse pin extending through the yoke and a portion of the boom arm. In such a case, the cylinder is disposed in the same vertical plane as the loader arm, and a relatively large yoke is required to transmit the forces involved. Also, the single thickness of the boom arm absorbs the entire load.
If the cylinders are connected to the boom arm mounting plates, then the mounting plates have to be relatively large and the welds extensive to accommodate the forces involved. This results in an expensive and heavy boom. If a boom weighs too much, the hydraulic cylinder can have difficulty controlling the boom during operation.
U.S. Pat. No. 4,798,512 shows a loader boom that is controlled by a pair of hydraulic cylinders acting between the main frame of the loader and a pair of parallel, transversely spaced boom arms that are interconnected by a transverse tube. A pair of tabs are respectively welded to the tube a short distance from the opposite ends of the tube, and the piston ends of the cylinders are respectively connected to the boom arms by a transverse pin extending through aligned bores in the tabs, eye members attached to the ends of the hydraulic cylinder piston rods, and the boom arms. However, in this design the boom is coupled directly to a bucket and both the boom and bucket cylinders are coupled to a vehicle frame part.